EDITOR'S NOTE: The following accounts were written at the 25th anniversary celebration of Vanguard I by some of the men who were there at the very beginning.

"The Legacy of Vanguard"

By Robert L. Tanner

There were some who called it "Project Rearguard," that heterogeneous team of technical and administrative people from government and industry whose hopes to launch the first American Earth satellite went up in a spectacular fireball on December 6, 1957.

There were calls for resignations, for congressional investigations of what incompetence or sabotage could have caused this blow to the national prestige in the wake of the Soviet Union's triumph a few months earlier. The Soviet feat was impressive, but it had been achieved with a massive military missile. The American goal had been to develop and employ an entirely new and completely non-military rocket to launch a satellite during the International Geophysical Year. But in the hue and cry following the Vanguard test failure, a vehicle assembled by the Army at its Redstone Arsenal was employed to launch the first American Earth satellite. A few months later, on March 17, 1958, the next Vanguard rocket launched the Vanguard I satellite to the greatest height ever reached by a man-made object—some 2,500 statue miles, placing it into an elliptical orbit with that height as an apogee and just over 400 miles as a perigee, the latter still exceeding any height previously reached.

On this 25th anniversary of that event, it is fitting to reflect on a few of its consequences and benefits. For more than a decade Vanguard 1, reportedly described by Soviet Premier Kruschev as "America's little grapefruit" has been the oldest man-made thing in the heavens (and will remain so for at least 1,000 years if not disturbed). It began yielding valuable scientific information almost immediately.

Project Vanguard's civil service personnel were transferred by an Executive Order of the President in 1958 into the newly created National Aeronautics and Space Administration (NASA) and a number of those from industry followed. The Vanguard team became the nucleus and cadre of the new Goddard Space Flight Center. At Goddard and other NASA installations, many of these same people still occupy key positions. Similarly many members of the industry team became important contributors to our nations space and defense programs. Other members of the Vanguard team moved on into new fields and endeavors. To all associated with Project Vanguard the events of 25 years ago not only left an indelible impression on theirs lives but started a legacy that still continues to this day.

"The Vanguard I Science Legacy"

by James W. Siry

This unprecedented record of scientific achievement, no less than half a dozen major findings, is even more remarkable when one realgizes that is was achieved using only data from Minitrack, the system whose primary function was originally envisioned as that of finding the IGY satellites and making possible orbit predictions for the Baker - Nunn cameras, whose role, in turn, was to provide the precise tracking data for scientific research. Minitrack and the Baker - Nunn both did indeed do their jobs over the next two decades, and in fact did them very well. As a bonus, Vanguard I and Minitrack also yielded the rich scientific harvest of the first years. Even just a single one of these many scientific discoveries would have earned Vanguard I its laurels as a scientific satellite. Its record of no less than half a dozen major scientific findings, with significant implications for upper atmosphere density, geodesy, geodynamics, solar terrestrial relationships, dynamical astronomy, and exospheric structure, was without parallel among the IGY spacecraft and, indeed, among all other satellites for some time afterward. Its scientific yield per unit mass was doubtless greater than for any other man-made object ever placed in space, a unique distinction which it will probably enjoy forever.

"The Minitrack Legacy"

by Chesley H. Looney, Jr.
Arial photo of a mintrack site
A Minitrack site.

The Minitrack system was the first world-wide tracking system implemented to support artificial satellite operations. It was based upon years of work in tracking rockets at White Sands, New Mexico, and was designed to impose minimum impact upon designers of the primitive satellites produced during the International Geophysical Year (IGY) (1957-58). The name Minitrack was coined by John T. Mengel as a contraction of the phrase "MINImum weight TRACKing system." Tracking achieved practical form in 1948 when engineers with Consolidated Vultee Aircraft Corporation (CONVAIR) created for the Army the Azusa tracking system, using an interferometer. Simultaneously with this development, Naval Research Laboratory (NRL) scientists were working with underwater sound interferometers. The two groups of experimenters were in close contact. They frequently exchange ideas, and in the early 1950's Milton Rosen and his NRL crew at White Sands built and field tested a tracking system, using the radio interferometer principle, for application to ballistic missile guidance for the Viking project.

For guidance purposes, the Azusa system had performed satisfactorily at White Sands and else-where. For tracking a satellite, however, it was out of the question since it required an airborne transmitter far too large for a small scientific payload weighing no more than 30 pounds, if that much. Refinements and modifications were indicated, and Mengel and his assistants shortly came up with an arrangement for that, although based on the Viking radio interferometry techniques, required instead of a heavy transporter only a 13-ounce transmitter and employed different operating frequencies and antenna configurations. It was in essence a new system.

Map showing Minitrack station locations
Minitrack station locations.

By December 1955, plans were virtually complete for the new Minitrack system. A north-south fence of stations would be built along the 75th meridian using antennas with fan-shaped beams making arcs of 100 degrees in the north-south direction and 10 degrees in the east-west direction. The development of the Minitrack electronics system was, indeed, at the "cutting edge" of the technology in 1956. Accurate timing systems were required; timing systems providing accuracies of a millisecond per day. The best crystal oscillations available had stabilities of about 1 in 100 million and were used in Loran-C navigation systems. Digital clocks, however were virtually un-known and were designed and built specifically for the Minitrack System. Their calibration, using NBS's radio station WWV was carefully defined with the assistance of NRL and NBS experts. The special double local oscillator receivers, based on the Azusa experience, were designed using the very best low noise vacuum tubes and techniques in order to require the smallest possible power levels from the satellite transmitters. The signal processing systems, a specially designed phase meter, was to provide phase measurement stability of a part in a thousand with detected signal amplitude variations of greater than 20 db. Post detection filter design considered both voltage and tempera- ture coefficients of inductance in the selection of components. Antenna design and selection of transmission lines were chosen to preserve as constant phase angle stability as the state-of-the-art would permit. Antenna layout was chosen to use the fewest number of antennas with spacing carefully selected to resolve ambiguities and provide the required geometrical angular accuracy in order to obtain orbital accuracies consistent with overall Project Vanguard goals.

Diagram of rocket with Vanguard satellite positioned in the nose.
Diagram of rocket with Vanguard satellite positioned in the nose.

Those of us lucky enough to have been on the Minitrack development team will forever cherish the guidance given by Jack Mengel, Buck Schroeder and Roger Easton in this grand effort. The fundamental wisdom they brought to bear on the many problems and their ability in electronics, physics and engineering stood the test of time. The Minitrack system, placed in operation in October 1957, served as the primary satellite tracking system for more than 23 years. When the last Minitrack system was turned off December 31, 1980, the original phase meters, using 12AU7 twin triode vacuum tubes, were still providing accurate data. Electronics had moved from tubes to transistors to integrated circuits while the many different circuits of the original Minitrack system not only achieved all its original goals, but also provided a rich source of scientific information as well. The pear-shaped earth was discovered through analysis of Vanguard I Minitrack data, as were important new facts about the earth's atmosphere. The legacy of Minitrack is also a rich source. There is a camaraderie among those of us involved in that pioneering effort that is precious. There is a fundamental lesson that a carefully designed system, tested under all conceivable conditions, with all interfaces specified, signal ranges Minitrack station locations. Diagram of rocket with Vanguard satellite positioned in the nose. and thresholds exercised, will perform satisfactorily, offer no surprises, and be absolutely dependable. There are many skilled professionals, trained in the Minitrack philosophy, working in NASA and in industry, still seeking the simplest, lowest cost solutions to difficult and complex problems. In this recognition of the 25th anniversary of the launch of Vanguard I, let us also recognize the efforts of the Minitrack pioneers, years of our spaceflight endeavors.